132 FXUS66 KPQR 011031 AFDPQR Area Forecast Discussion National Weather Service Portland OR 331 AM PDT Fri Jul 1 2016 .SYNOPSIS...A persistent weather pattern will result in coastal low clouds spreading inland each night with clearing in the afternoons. A couple of weak upper level disturbances will produce light drizzle or rain along the coast and northern areas at times. Temperatures will remain near early July normals today and Saturday, then trend a little cooler early next week as a flat upper level trough settles into western Canada and Washington. && .SHORT TERM...(Today through Sunday Night)...Typical early summer onshore flow pattern persists today, with stratus gathering along the Washington and northern Oregon coasts. The moist onshore flow, powered by gradients still about +7 mb from KAST-KPDT, is also causing some low clouds to develop in the foothills of the S WA Cascades and Mount Hood. Expect low clouds to continue to fill in this morning north of a Tillamook to Mt Jefferson line, though a few gaps will probably remain by sunrise. Present expectation is that areas south of Salem will stay mainly clear this morning due to a greater northerly component to the pressure gradients cutting off the source of moisture in the boundary layer. For the north, low clouds should clear back to the coast around midday, with plenty of afternoon sunshine inland. High temperatures today should overall be very similar to yesterday and close to seasonal norms...generally close to 80 for most inland valleys. Persistence pattern continues into Saturday, with perhaps a little more low cloud coverage due to a weak shortwave developing offshore and shown by the 00z GFS/ECMWF to move across WA Sat AM. The shortwave may encourage a little drizzle to fall out of the stratus, mainly in our northern coastal and higher terrain zones. Slightly more widespread and persistent clouds may cause temps to be a couple degrees cooler than today. The gradual cooling trend looks to continue into Sunday as a more significant shortwave and associated cold front move across WA and NW Oregon. Sunday morning will probably have the best chance of drizzle or light rain out of the next three, with fairly widespread low clouds extending inland all the way down to Eugene. Again the best chance for -DZ/-RA will be along the north coast and higher terrain, but a couple spits of -DZ/-RA cannot be ruled out for the PDX Metro Sunday morning, especially closer to the foothills. Stubborn low clouds should give way to some afternoon sunshine, but a cooler air mass and fewer hours of sunny skies will probably knock temperatures down a few more degrees...perhaps even a couple degrees below normal in some areas.Weagle .LONG TERM...(Monday/Independence Day through Thursday)...Slow transition to below normal temps is likely to continue Mon/Tue, with a longwave trough axis settling into the Pac NW. Ironically, the upper trough may actually help the chances for clear skies in the low levels the evening of the 4th, even along the coast, due to cooler air aloft weakening the marine inversion...possibly enough to scatter out the coastal stratus. 00z GFS/ECMWF do bring a stronger shortwave onshore Mon afternoon/evening, which could produce some clouds itself and perhaps a stray shower or two north of Portland. Reinforcing shot of cool air behind this system will likely keep temps below normal into mid-week. Model and ensemble agreement then falls apart Thu/Fri, with some members suggesting a ridge will try to build northward from California. However the majority opinion of the models/ensembles keep the Pac NW under somewhat of a trough for near to below normal temps for the rest of the week. 00z ECMWF operational run even brings a strong enough frontal system onshore to bring a threat for rain Thursday, though we discounted this solution for the time being, as it is a bit of an outlier and climatological PoPs are very low this time of year anyway. Weagle && .AVIATION...VFR conditions prevailing today and evening with increasing chances for MVFR later tonight and Sat. Expected to see some MVFR CIGS ranging from 1500 and 2500 feet extending from the Cascade Foothills north of KSLE to the coast this morning. KAST area may occasionally see MVFR cigs mixed with VFR conditions through early afternoon while the remainder of the coast should remain VFR. More widespread MVFR CIGS return this evening the spread inland overnight as a weak upper trough shifts across the area. KPDX AND APPROACHES...VFR conditions today through most of tonight. However there is a good chance for some MVFR stratus around 2000 feet through 16Z. MVFR CIGS likely to return after 08Z Sat. mh && .MARINE...Typical summer-time pattern continues with high pressure over the WA and OR waters and a thermal low over California. A weak front to move across the waters today and tonight will interrupt this pattern which will weaken the northerly winds today and Saturday. Next chance for advisory winds will probably be on Sunday afternoon and evening as high pressure strengthens over the waters. Northerly winds looks to continue into next week. Seas are a mix of steep wind waves and small fresh well, although a small background long-period south swell also occasionally becomes noticeable as well. The seas will generally hover between 3 and 5 ft today with larger swell tonight and Saturday with seas building seas up to around 5 to 7 ft through early next week. Seas fall back down to 4 to 5 ft by midweek next week. mh && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...None. && $$ Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland This discussion is for Northwest Oregon and Southwest Washington from the Cascade crest to 60 nautical miles offshore. The area is commonly referred to as the forecast area.
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